sedimentary

Chert (Jasper/Quartzite river pebble)

Microcrystalline Silica (SiO2)

Hardness: 6.5-7 Mohs; Color: Brown, tan, and grey with iron staining; Luster: Dull to waxy; Crystal structure: Hexagonal (microcrystalline); Cleavage: None (conchoidal fracture); Specific gravity: 2.65.

Hardness: 6
Color: Brown, tan, and grey with iron staining
Luster: Dull to waxy

Identified April 1, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed as a chemical precipitate or through the replacement of limestone by silica-rich fluids. This specific specimen has been physically weathered and rounded by water transport in a river or coastal environment over thousands of years.

Uses & applications

River pebbles like this are used in landscaping, road construction (as aggregate), and occasionally as lapidary material for tumbling if they contain high-quality Jasper.

Geological facts

Chert was one of the most important tools for early humans; its conchoidal fracture creates sharp edges perfect for arrowheads and scrapers. The brown/orange coloration in this pebble is likely due to iron oxide staining during the weathering process.

Field identification & locations

Identify in the field by its hardness (it will scratch glass), rounded 'egg-like' shape indicating water transport, and waxy texture. Commonly found in riverbeds, glacial tills, and beaches.

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